Conventional electrowetting based liquid lenses are based on two immiscible liquids disposed within a chamber, namely an oil and a conductive phase, the latter being water based. The two liquid phases typically form a triple interface on an isolating substrate comprising a dielectric material. Varying an electric field applied to the liquids can vary the wettability of one of the liquids relative to walls of the chamber, which has the effect of varying the shape of a meniscus formed between the two liquids. Further, in various applications, changes to the shape of the meniscus result in changes to the focal length of the lens.
Water is generally used as the main component of the conductive phase because water provides a highly polar component that can readily dissolve salts. However, among the drawbacks of water based conductive phases are the volatility of water, particularly when the electrowetting device is used in warm or hot environments where risks of corrosion can degrade both the oil liquid phase and the electrowetting device itself. Additionally, for liquid lens applications, the use of water frequently leads to its slow evaporation over time and leakage of water outside the liquid lens. As a consequence, when too much water is lost, an air bubble will appear in the liquid lens, which renders the lens ineffective. Finding an oil that is resistant to the corrosive aqueous conductive phase while also providing refractive index and other desired properties is needed.
Accordingly, there is a need for liquids used in liquid lens configurations to provide improved chemical and temperature stability, which can translate into improved liquid lens reliability, performance, and manufacturing cost.